13th International Conference on Fracture June 16–21, 2013, Beijing, China -3- (1/λs vs 1/L) are plotted and extrapolated in Fig. 2. Figure 2. The inverse of the thermal conductivities for amorphous silica systems and their linear extrapolation to infinite lengths This method gives values of 2.13W/(m.K) for the BKS potential, and 1.19W/(m.K) for the Tersoff potential, at bulk length scales. This gives an error of 55% overestimation for the former, and 13% underestimation for the latter, clearly showing that the re-parameterized Tersoff is much more capable of reproducing bulk thermal properties than the BKS potential can. This is analyzed further by examination of the vibrational density of states (vDOS) of each potential, as shown in Fig. 3, which are obtained through the discrete Fourier transform of the velocity autocorrelation function (VACF) [20]. Figure 3. vDos of a) BKS, and b) Tersoff potential The Tersoff potential clearly shows, as shown in Fig. 6b, the same peaks near the frequencies of 10.5THz, 24.0THz and 36.0THz determined from previous experimental and theoretical results by Laughlin et al. [21]. However, the BKS potential, in Fig. 6a, showes no apparent peaks below the 30THz region. Thus, from all these methods presented, we can conclude that the re-parameterized Tersoff potential is a far superior alternative in the thermal characterization of bulk amorphous
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